Continuous Textile Converting Method and Installation Therefor

ABSTRACT

The invention concerns a method for continuously converting textile materials by passing same in a microwave field and contacting same with a surface capable of being heated. The inventive method consists, after depositing treating agents on said textile material, in: continuously passing the textile material and its deposited treating agents inside a chamber; applying inside the chamber a microwave radiation at atmospheric pressure; contacting inside the chamber the textile material with a surface capable of being heated; extracting the steam from inside the chamber throughout retention time of the textile material in the chamber.

The present invention concerns a continuous ennobling process with or without tension of textile material by passage through a microwave field and contact with a heatable surface. The other object of the invention is an installation to implement thesaid process.

In France, the ennobling industry uses every year some 50 million m³ of water, which must then be cleaned before being rejected into the natural environment (European directive 21/271/EEC of 21 May 1991).

In classical dye processes, the large quantities of treated water used generate large quantities of waste water. The cost of pollution control is often exorbitant for such companies.

Furthermore, these large volumes of water are heated for many hours, resulting in high levels of energy consumption.

Different types of textile material ennobling processes have been proposed with the aim of reducing the quantity of water necessary for the treatment of textile materials and/or the duration of treatment and/or the quantity of energy consumed during such treatments.

Some of these processes use microwave technology owing to its numerous advantages:

-   -   microwaves immediately penetrate textile materials and induce         very rapid heating of such material since, as opposed to all         other means of heating, heating in this case does not depend on         thermal conductivity; this results in a substantial time gain;     -   they ensure even heating of the textile material;     -   they allow controlling the interactions between the textile         material and treatment reagents according to the treatment         applied to the textile material by simple regulation of the flux         as a function of textile material weight;     -   there is no energy loss by thermal radiation, which results in         economic gains and better working conditions.

The present invention aims to propose a textile material ennobling process that allows a reduction in water pollution at the source by limiting water, energy and dye auxiliary consumption.

To this effect and according to a first aspect, the invention relates to a continuous textile material treatment process comprising a step to deposit the treatment agent on thesaid textile material, characterized in that it comprises the following steps:

-   -   making the textile material and its treatment agent deposit pass         continuously through an enclosure;     -   applying microwave radiation at atmospheric pressure inside the         enclosure;     -   placing the textile material in contact with a heatable surface         inside the enclosure;     -   extracting the water vapour from inside the enclosure while the         textile material is maintained inside the enclosure.

According to certain embodiments, the deposit step comprises a step of impregnation of thesaid textile material in a bath containing the required treatment reagents and a wringing step until a given dye exhaust percentage is obtained. The textile material is impregnated with reagents and wrung so as to obtain a dye exhaust percentage between 40 and 200%.

According to other embodiments, the deposit step comprises a printing step of thesaid textile material.

The microwave radiation power depends on the weight of the textile material being treated and is comprised between 0.8 and 3 kWh per kg of textile material treated. The time during which the textile material is maintained in the enclosure is in the order of 60 s to 240 s. This length of time can be modulated according to the quality and nature of the material.

Preferably, thesaid heatable surface is the external surface of the rotating cylinder. Its temperature can be brought up to 210° C.

According to a second aspect, the object of the invention is an installation for the continuous treatment of textile material comprising means of depositing treatment agents onto thesaid material, characterized in that it also comprises:

-   -   an enclosure comprising an inlet opening and an outlet opening         for the material;     -   means of applying microwave radiation on the textile material         inside the enclosure;     -   a heatable surface that comes in contact with the material while         the latter is moving inside the enclosure;     -   means of extracting the water vapour formed inside the         enclosure;

The invention is now going to be described in detail.

The present invention aims to provide a textile material ennobling process allowing a significant reduction in the quantities of water and energy used, in the duration of treatment and in the rejection of effluents.

Textile material ennobling, which comprises all the treatments textile material is subjected to in order to improve its aspect and properties, can be divided into three stages: pre-treatment, dyeing and after-treatment.

Pre-treatment is designed to prepare textile materials so as to make them white, ready for dyeing or give them particular properties.

The process according to the invention also allows performing various after-treatments such as drying, stiffening and softening.

The process according to the invention can be employed for the preparation, dyeing, printing and after-treatment of all textile materials whether natural, artificial or synthetic.

In an alternate embodiment, the textile material is first of all plunged according to the type of operation in a bath containing the reagents necessary for the treatment chosen: boiling off, whitening, dyeing, and finishing by wet laying. The baths used can be worked out from dye specification sheets using appropriate quantities for very short bath ratios.

After impregnation, the textile material is wrung out in order to obtain a dye exhaust percentage between 40 and 200%.

Numerous auxiliary dye products, such as vehicles, dispersing agents, levelling agents, wetting agents, yield enhancing agents, antifoam agents, urea, were successfully removed from the bath using microwaves.

In another embodiment, printing of the textile material is first of all achieved with a printing paste or inks in order to obtain a pattern.

The textile material is then introduced into an enclosure inside which microwave radiation is applied.

The microwave field is generated by one or several magnetrons of known type in order to obtain sufficient power for the quantity of textile material to be treated, at the desired treatment speed (the electromagnetic radiation energy required is between 0.8 and 3 kWh per kg of material). The duration of microwave treatment can vary between 60 and 240 seconds.

The textile material is placed in contact with a heatable surface inside the enclosure while being exposed to microwave radiation. The textile material travels at a known speed, which depends on the length of the path in the enclosure.

In a preferred embodiment, the textile material is placed inside the enclosure, in contact with a surface heated to a temperature comprised between 40 and 210° C. depending on the type of treatment and nature of the textile material to be treated. This makes it possible to obtain a synergistic effect between the action of the microwave and the thermal energy radiating from thesaid surface, which helps obtain the technical sought effect corresponding to the treatment applied to the textile material, while limiting the duration of treatment and water, energy and dye auxiliary consumption.

In another embodiment, the process of the invention is implemented without heating thesaid surface, its temperature remaining at room temperature (from 20 to below 40° C.). This case applies in particular to the dyeing of cotton using direct dyes.

In a preferred embodiment, the heatable surface is the outer surface of the rotating cylinder.

The time during which the textile material is maintained in the enclosure, which corresponds to the time required to apply the microwave radiation, is comprised between 60 and 240 seconds.

The process of the invention also comprises a step to extract the water vapour formed inside the enclosure during microwave radiation treatment. This is performed by means allowing water vapour aspiration such as a depression-generating device.

The process may also involve mixing of the microwave radiation inside the enclosure in order to avoid the appearance of stationary waves.

The process is suitable for applying chemical treatments (textile material preparation and after-treatment) as well as dye stuffs. Such textile material may take various forms such as threads, yarns, as well as woven, non-woven, felt and knitted textile materials). The dyeing or printing performed using this process is applicable to all the usual classes of dyes and any type of fibres.

Concerning the treatment of cellulose fibres, it takes into account materials made of regenerated cellulose and natural cellulose. Hence, viscose, hemp, linen, jute and cotton, for instance, as well as textile material mixtures such as cotton/polyester/spandex can be treated.

In order to boil off such materials, a bath is used containing a wetting detergent resistant to basic pH as well as an alkaline agent in an amount that varies according to the level of impurity of the material to be treated.

The whitening of cellulose materials is achieved in the presence of an oxidizing agent (hydrogen peroxide), an alkaline agent (pH between 9 and 11) and an agent to stabilise the hydrogen peroxide. In order to obtain a higher degree of whiteness, it is possible to add an optical brightener to the whitening bath or to brighten the material after whitening.

The dyeing of cellulose materials can be achieved with dyes such as direct dyes and reactive dyes. Other dyes such as sulphur dyes can also be used, after modification. Dyeing with active dyes is carried out in an alkaline medium. The bath must be in a pH range of 9 to 12. The use of a yield enhancing agent is usually required. Sulphur dyes are introduced into the impregnation bath in their soluble form. The bath contains a reducing agent in order to keep them in this form and an alkaline agent to maintain the pH between 10 and 12.

The quantity of dye introduced in the bath depends on the colour depth required and the solubility limit of each agent under the operating conditions at hand.

The treatment of synthetic fibres such as polyamide 6 and 66, natural fibres such as wool or silk, or mixtures of fibres containing these materials can be performed using the same method.

For wool degreasing, the bath may contain an alkaline agent in order to obtain a pH between 8.5 and 9.5, and an appropriate detergent. Natural polyamides may require whitening. The oxidizing whitening bath contains an oxidizing agent such as hydrogen peroxide, an alkaline agent and a stabilizer. The reducing whitening bath contains a reducing agent such as sodium dithionite. These whitening agents are introduced in the bath in varying amounts according to the type of polyamide being treated.

The dyeing of polyamide materials can be performed using anionic dyes such as acid, metalliferous 1/1 and 1/2, or reactive dyes. Dyeing is performed in acid medium (pH comprised between 3 and 7). Synthetic polyamides can be dyed with cationic or dispersed dyes.

Dyeing of synthetic fibres can also be achieved with this process using dispersed dyes in slightly acid medium (pH between 5.5 and 6.5). In the majority of cases, addition of an anti-migration agent is necessary. Reductive cleaning of the polyester after dyeing, for instance, can also be achieved by this process using an alkaline bath containing sodium dithionite.

The process is also applicable to the dyeing of mixtures. Thus, material made of cotton and polyester, or wool and polyester, for instance, or any other mixture can also be treated. In addition, the process allows treating materials containing spandex. The materials are treated under operating conditions that do not alter the properties of spandex.

Auxiliary dye products may be added in small quantities to the treatment bath as a function of the specificities of each material.

The present invention will be more thoroughly understood upon reading the following examples, given as non limiting instances in view of illustrating better the characteristics of the textile material ennobling process that is the object of the present invention.

EXAMPLE 1 Boiling Off of Cotton

A 100% raw cotton textile material of 120 g/m² is impregnated at 25° C. in a bath containing:

-   -   10 g/l of wetting detergent such as mercerisin OR     -   150 ml/l 30% sodium hydroxide     -   6 g/l sodium carbonate

The contact time with the bath is the time required for proper impregnation and the dye exhaust percentage is 70%. It is then exposed to a microwave field with a radiation power of 1200 W before being placed in contact with a surface heated to 50° C. while being subjected to microwave radiation treatment. Treatment time is 180 seconds. The textile material is then rinsed in a hot rinse followed by a cold rinse.

EXAMPLE 2 Cotton Dyeing with Reactive Dyes

A 100% cotton textile material of 120 g/m² previously boiled off and whitened is impregnated at 25° C. in a bath containing:

-   -   10 g/l of commercial reactive dye called Cibacrone red CR     -   6 ml/l 30% sodium hydroxide     -   10 g/l sodium carbonate     -   30 g/l sodium chloride

The dye exhaust percentage is 70%. The textile material is exposed to a microwave field with a radiation power of 1200 W, then placed in contact with a surface heated to 150° C. while undergoing microwave radiation treatment. The duration of treatment is 120 seconds. The textile material is rinsed with a cold rinse followed by a hot rinse then washed with soap and rinsed once again.

Comparison of Effluent Cod for Cotton Dyeing Using a Reactive Dye with the Classical Pad-Batch Process:

The bath used for the pad-batch process is the one recommended in the specification sheets:

-   -   20 g/l of dye (cibacrone red CR, cibacrone yellow CR, cibacrone         blue CR)     -   70 ml/l sodium silicate     -   6 ml/l sodium hydroxide     -   storage without heating for 24 hours.

Effluent COD from the pad-batch process was compared with that resulting from cotton dyeing using the present invention. The results are presented in diagram 1, where dark bars refer to the pad-batch process and light bars to the process of the present invention.

These results show that for the yellow and blue dye, effluent COD for the process of the present invention is significantly reduced as compared to the classical pad-batch process.

EXAMPLE 3 Dyeing of Polyester in Dispersing Dyes

A 100% polyester textile material of 290 g/m² is impregnated at 50° C. in a bath containing:

-   -   10 g/l of commercial dispersing dye called Foron red RD-GL     -   1 ml/l acetic acid     -   10 g/l of an anti-migration agent such as Solidokol K

The dye exhaust percentage is 70%. The textile material is exposed to a microwave field with a radiation power of 1200 W and then placed in contact with a surface heated to 180° C. while undergoing microwave radiation treatment. The duration of treatment is 120 seconds. The textile material is then rinsed, cleaned by reduction and then rinsed one more time. Reductive cleaning, which allows eliminating unfixed dye, was carried out in a vat or using the present invention. The results obtained are presented in table 1. TABLE 1 Reductive cleaning using the process of Reductive cleaning in a vat the present invention 3 g/l sodium dithionite 40 g/l sodium dithionite 3 g/l sodium hydroxide 40 g/l sodium hydroxide 1/20 bath ratio Percent dye exhaut: 60% Treatment duration: 20 min. Surface temperature: 180° C. at 90° C. Treatment time: 120 seconds Effluent COD Effluent COD Effluent COD Effluent COD before effluent after effluent before effluent after effluent treatment: treatment: treatment: treatment: 711 mg O₂/l 539 mg O₂/l 83 mg O₂/l 43 mg O₂/l These results show there is a significant effluent COD reduction in effluents from reductive cleaning according to the present invention as compared to reductive cleaning by the vat method.

EXAMPLE 4 Wool Dyeing Using Acid Dyes

A 100% wool previously degreased material of 310 g/m² is impregnated at 50° C. in a bath containing:

-   -   10 g/l of solid commercial acid dye called Erio floxine KL     -   4% sulphuric acid (per weight of textile material).

The contact time with the bath is 5 seconds and the dye exhaust percentage is 80%. The textile material is exposed to a microwave field with a radiation power of 1200 W and then placed in contact with a non heated surface while undergoing microwave radiation treatment. The duration of treatment is 120 seconds. The textile material is then rinsed.

EXAMPLE 5 Cotton Dyeing Using Direct Dyes

A 100% cotton textile material of 120 g/m², previously boiled off and whitened, is impregnated at 25° C. in a bath containing:

-   -   40 g/l of commercial direct dye called Sinius orange 3 GDL.

The dye exhaust percentage is 50%. The textile material is exposed to a microwave field with a radiation power of 1200 W and then placed in contact with a non heated surface while undergoing microwave radiation treatment. The duration of treatment is 120 seconds. The textile material is then rinsed with a cold rinse followed by a hot rinse and then washed with soap and rinsed one more time.

EXAMPLE 6 Dyeing of a Cotton/Polyester (50/50) Mixture Using Active and Dispersed Dyes

An article of knitwear made of 50% cotton and 50% polyester of 200 g/m², previously boiled off and whitened, is impregnated at 25° C. in a bath containing:

-   -   15 g/l of 200% commercial dispersed dye called Foron red RD GL,     -   1 ml/l acetic acid,     -   10 g/l Solidokol K.     -   The dye exhaust percentage is 70%. The knitwear is exposed to a         microwave field with a radiation power of 1200 W and then placed         in contact with a surface heated to 150° C. while undergoing         microwave radiation treatment. The duration of treatment is 240         seconds. The textile material is then rinsed, cleaned by         reduction and rinsed again.

It is then impregnated at 25° C. in a bath containing:

-   -   30 g/l of commercial reactive dye called Cibacrone blue CR     -   10 g/l sodium carbonate,     -   6 g/l sodium hydroxide,     -   30 g/l sodium chloride.

The dye exhaust percentage is 70%. The knitwear is exposed to a microwave field with a radiation power of 1200 W and then placed in contact with a surface heated to 150° C. while undergoing microwave radiation treatment. The duration of treatment is 120 seconds. The textile material is then rinsed, washed with soap and rinsed again.

EXAMPLE 7 Printing of cotton using reactive dyes

A 100% cotton textile material of 120 g/m², previously boiled off and whitened, is printed at 25° C. using a paste containing:

-   -   40 g/kg sodium alginate,     -   20 g/kg sodium carbonate (Na₂CO₃)     -   2 ml/kg sodium hydroxide (NaOH) at 36° Be,     -   25 g/kg of dye,     -   Water gsp for 1 Kg of textile material.

The textile material is printed using a rotating frame. A 2-bar pressure is exerted on the doctor blade. The textile material is exposed to a microwave field with a radiation power of 1200 W and then placed in contact with a surface heated to 150° C. while undergoing microwave radiation treatment. The duration of treatment is 120 seconds. The textile material is then rinsed with a cold rinse followed by a hot rinse, washed with soap and rinsed again.

According to a second aspect, the object of the invention is an installation for the continuous treatment of planar textile material comprising either the means to impregnate thesaid material and the means to wring it, or the means to print it, characterised in that it also comprises:

-   -   an enclosure comprising an inlet opening and an outlet opening         for the material;     -   means of applying microwave radiation to the textile material         inside the enclosure;     -   a heatable surface that comes in contact with the material while         the latter is moving inside the enclosure;     -   means of extracting the water vapour formed inside the         enclosure.

In one embodiment, the agent depositing means comprise the means to impregnate and the means to wring thesaid material.

In another embodiment, the agent depositing means include means of printing.

The temperature of thesaid surface is comprised between 20 and 210° C. The surface may or may not be heated depending on the type of textile material to be treated. The heatable surface is placed in contact with the textile material, which travels at a given speed as a function of the path length in the enclosure.

The time during which the textile material is maintained inside the enclosure, which corresponds to the duration of the microwave radiation treatment, is comprised between 60 and 240 seconds.

Preferably, the heating surface is the outer surface of a rotating cylinder.

In one embodiment, the cylinder is made of amagnetic metal that is inert with respect to the chemicals introduced in the bath and may be coated with PTFE.

The material is made to enter and exit via slits of suitable shape in order to avoid any wave propagation to the outside.

The means used to extract the water vapour formed inside the enclosure are those known to people experienced in this art, such as a depression-generating system or a ventilation system.

The installation according to the invention may comprise means of mixing the microwave radiation inside the said enclosure. 

1. Process for the continuous treatment of textile material, comprising a step to deposit treatment agents onto thesaid textile material, characterised in that it involves the following steps: making the textile material and the deposit of treatment agents travel continuously inside an enclosure; applying a microwave radiation treatment at atmospheric pressure inside the enclosure; placing the textile material in contact with a heatable surface inside the enclosure; extracting the water vapour from inside the enclosure while the textile material is maintained in the enclosure.
 2. Process according to claim 1 characterised in that the deposit step comprises a step of impregnation of thesaid textile material in a bath containing the necessary treatment reagents and a wringing step until a given dye exhaust percentage is obtained.
 3. Process according to claim 2 characterised in that the textile material is impregnated with reagents and wrung in order to obtain a dye exhaust percentage comprised between 40 and 200%.
 4. Process according to claim 1 characterised in that the reagent deposit step comprises a step of printing of thesaid textile material.
 5. Process according to any one of claims 1 to 4, characterised in that the microwave radiation power is comprised between 0.8 and 3 kWh per kg of textile material treated.
 6. Process according to any one of claims 1 to 4 characterised in that the time during which thesaid textile material is maintained inside the enclosure is in the order of 60 to 240 seconds.
 7. Process according to any one of claims 1 to 4 characterised in that the temperature of thesaid surface is comprised between 40 and 210° C.
 8. Process according to any one of claims 1 to 4 characterised in that thesaid surface is at room temperature.
 9. Process according to any one of claims 1 to 4 characterised by the mixing of microwave radiations inside the enclosure.
 10. Process according to any one of claims 1 to 4 characterised in that the heatable surface is the outer surface of the rotating cylinder.
 11. An installation for the continuous treatment of a textile material comprising means to deposit treatment agents on thesaid material, characterised in that it also comprises: a) an enclosure comprising an inlet opening and an outlet opening for the material; b) means of applying microwave radiation to the textile material inside the enclosure; c) a heatable surface that comes in contact with the material while the latter is moving inside the enclosure; d) means of extracting the water vapour formed inside the enclosure.
 12. An installation according to claim 11 characterised in that the means for agent depositing comprise means for impregnation and ringing of thesaid material.
 13. An installation according to claim 11 characterised in that the agent depositing means comprise printing means.
 14. An installation according to any one of claims 11 to 13 characterised in that the heatable surface is the outer surface of the rotating cylinder.
 15. An installation according to any one of claims 11 to 13 characterised in that thesaid surface is an amagnetic surface that is inert with respect to the chemicals used.
 16. An installation according to any one of claims 11 to 13 characterised in that thesaid surface is coated with PTFE.
 17. An installation according to any one of claims 11 to 13 characterised in that the shapes of the inlet and outlet openings are made in such a way as to prevent microwave leakage.
 18. An installation according to any one of claims 11 to 13 characterised in that it comprises means of mixing microwave radiation inside thesaid enclosure.
 19. An installation according to any one of claims 11 to 13 characterised in that the means used to extract the water vapour formed inside the enclosure comprise either a depression-generating system or a ventilation system. 